The overproduction of leukotrienes (Lts) is central to the pathogenesis of several inflammatory and allergic disease states, including asthma. The enzyme 5-lipoxygenase (5-LO) catalyzes the initial steps in LT synthesis from arachidonic acid. Thus, delineating its regulation is essential to understanding the basis for LT overproduction. Thus, delineating its regulation is essential to understanding the basis for LT overproduction. Recent studies have shown that 5-LO is found within the cytoplasm of circulating leukocytes and that nuclear import of 5-LO can be triggered by cell adhesion, recruitment into sites of inflammation and exposure to cytokines. However, the molecular regulation of 5-LO subcellular localization is poorly understood, and the consequences of redistribution of 5-LO within the cell, particularly in terms of its effect on LT synthesis, remains unclear. The long-term objectives of this project, then, are to understand the mechanisms that regulate 5-LO subcellular distribution and how 5-LO movement might contribute to disease pathogenesis, particularly via LT overproduction in the context of inflammatory and allergic diseases. The specific aims of this project are 1) to characterize the regions within the 5-LO protein that are essential for nuclear import and export, 2) to define the role of protein phosphorylation in the regulation of 5- LO movement, 3) to determine how 5-LO localization, as regulated by nuclear import and export sequences and protein phosphorylation, affects LT synthesis, and 4) to determine the effect of 5-LO localization on cell viability. These studies will provide the foundation for a better understanding of the cellular, molecular and genetic factors involved in 5-LO localization and LT synthesis. This foundation can then be used to elucidate the ways these factors can change and give rise to the disease states that arise from abnormal 5-LO localization and LT synthesis.